1. Field of the Invention
The invention relates to a method of manufacturing a replicated magnetic reproduction medium, such as a magnetic-tape cassette provided with a music recording, which reproduction medium comprises a magnetic tape having a plurality of tracks extending parallel to one another in the longitudinal direction at specified spacings within certain limits from one another, which reproduction medium serves for the reproduction of the replicated signals by means of a magnetic reproducing head having a plurality of transducing gaps situated at specified spacings within certain limits from one another with a specified normal tape tension within certain limits, which method comprises the transport of the tape during the replication over a head face of a magnetic replication head also having a plurality of transducing gaps with a certain spacing from one another.
2. Description of the Related Art
It is known (see Philips Technical Review, Vol. 31, 1970, No. 3, herewith incorporated by reference) to provide Compact Cassettes with a music recording in the manner described. The replicated media are generally referred to as Music Cassettes. During replication a magnetic tape having a width of 3.81 mm is moved past a replication head with a speed which is 32 or even 64 times the normal reproduction speed. Four juxtaposed parallel tracks are recorded on the tape simultaneously, i.e. two tracks in the A-sector to be played in the forward direction and, at the same time, two tracks in the B-sector of the tape, to be played in the reverse direction. In accordance with the standard for the Compact Cassette System (see Publication 94-7 of the Bureau Central de la Commission Electrotechnique Internationale, 3 Rue de Varembe, Geneva, Switzerland, herewith incorporated by reference) the width of each track is 0.62 mm. The spacing between two tracks in the same sector is 0.3 mm. The spacing from the adjacent tracks in the A-sector or the B-sector is 0.66 mm.
The use of a transport speed for replication which is substantially higher than the normal reproduction speed is of great importance in order to realize a method which can be carried out on industrial scale at reasonable cost.
The Compact Cassette system is a so-called analog recording/reproducing system, i.e. the signals recorded on the tape are of an analog nature. Since some time, a new digital recording/reproducing system related to the Compact Cassette system has attracted much attention: the so-called Digital Compact Cassette system or DCC. In view of this, the well-known analog Compact Cassette system is now often referred to by the abbreviation ACC: Analog Compact Cassette system.
In the same way as in the well-known ACC system, the tape in the DCC system also has an A-sector to be played in the forward direction and a B-sector to be played in the reverse direction. However, each sector now comprises nine parallel tracks, i.e. eight parallel digital audio tracks and one digital auxiliary track. This means that there are nine tracks in each sector and eighteen tracks in total. The magnetic tape being used has a width substantially equal to that of ACC, i.e. 3.78 mm. Consequently, the width of the tracks and the intertrack spacing in the DCC system is substantially smaller than in the ACC system.
The width of the tracks specified for DCC for replicated music recordings is 0.185 mm. The specified distance from one edge of a track to a corresponding edge of an adjacent track in the same sector is 0.195 mm. When such narrow tracks and such small intertrack spacings are used a very good guidance of the magnetic tape over the magnetic head during reproduction is essential in order to achieve that the transducing gaps of the magnetic head are situated exactly at the location of the tracks on the tape. In the DCC system one edge of the tape is therefore held in contact with a tape guide during playing, see the Applicant's earlier European Patent Application 91203255.4 ([PHN 13907], herewith incorporated by reference). Although the tolerances on the track width and the intertrack spacing in the DCC system are very small, yet due to the large number of tracks the resulting total tolerance range with respect to the position of the track which is remotest from the tape guide will be substantial in comparison. Therefore it is possible only with difficulty to ensure that during reproduction the track which is remotest from the tape guide can actually be read by the transducing gap of the reproducing head. Variables of different nature will influence the positions of the tracks relative to the associated transducing gaps of the magnetic head. These variables include, for example, temperature, undulation of the edge of the magnetic tape, differences between the tape guides of the replication arrangement and the reproducing apparatus, similar differences in the positions of the transducing gaps of the magnetic heads of the replication arrangement and the reproducing apparatus, tape-width tolerances, etc. In addition, there are differences in tape stretch and hence in transverse contraction of the tape during replication and playing of the tape. It is important that also during replication the position of the tape in relation to the head gaps of the replication head is accurately adjusted and the adjusted position is subsequently maintained.
In order to guarantee proper contact between a magnetic tape and a magnetic head and hence a correct signal transfer the tape must be pressed against the head face of the magnetic head with a specific force. Therefore, a certain tension is maintained in the tape during reproduction, while in addition, the tape is pressed against the head face by a pressure felt. In replication arrangements, the use of a pressure felt is undesirable, inter alia in view of the high speed of transport of the tape.